Various surgical procedures require interrupting the normal functioning of the heart and lungs of the patient. Some of the functions of these organs are temporarily replaced by an extracorporeal blood handling system. The main volume of the patient's blood, known as the venous return stream, is typically withdrawn from the patient through a venous cannula inserted into the right atrium. The blood handling system collects the volume of blood in a venous reservoir. The blood handling system serves to pump the blood, regulate the carbon dioxide and oxygen content, regulate the temperature, defoam and remove emboli and particulate matter using one or more filters. The blood is then returned to the patient through an aortic cannula inserted into the aorta distal to the heart.
Blood from the surgical field, known as cardiotomy blood, is typically drawn into a cardiotomy reservoir. The cardiotomy blood typically contains gas bubbles, fragments of tissue, bone chips, blood clots, surgical debris and other dangerous and undesirable contaminants. The cardiotomy reservoir defoams, filters and collects the cardiotomy blood prior to combining it with blood in the venous reservoir. The level of filtration required for cardiotomy blood is typically greater than that required for the relatively clean venous return stream.
The high level of filtration necessary for cardiotomy blood may cause damage to blood constituents, such as due to sheer stress. Consequently, cardiotomy blood filtration is preferably performed separately from filtration of the relatively clean venous return stream. Integrated cardiotomy reservoirs (ICR) combine the treatment of both cardiotomy and venous blood streams.
Turbulent flow may develop at various locations within the blood handling system. Turbulent flow can cause bubbles to form in the blood and can increase the blood-to-air contact. Blood to air contact causes hemolysis of red blood cells. Hemolysis refers to the lysis or destruction of erythrocytes with the release of hemoglobin, resulting in a reduction in the ability of the blood to carry oxygen.
Blood handling systems can also have locations of blood stasis that can cause blood clotting or separation of blood components. Medical care providers are increasingly interested in viewing the condition of the blood throughout the entire blood circuit. Current blood treatment systems typically have internal regions that are not visible to the medical staff, such as the interior of cylindrically shaped filter media. Areas within the blood handling system that cannot be viewed by the medical staff may result in undetected blood stasis or clots.
Typical blood handling systems have a large number of discrete parts, requiring manual assembly, increasing the risk of assembly errors and increasing manufacturing costs. Manufacturing a variety of distinct extracorporeal blood handling systems with different blood treatment elements increases manufacturing and inventory costs. Variability between products also raises the risk of errors in assembly or marketing of finished products, resulting in a potentially detrimental medical impact on the patient.